(a) Field of the Invention
The present invention relates to a handover method for a terminal in a mobile communication system.
(b) Description of the Related Art
LTE (Long Term Evolution) mobile communication systems are in commercial use and provide services throughout the world. In LTE, a terminal performs a handover when moving from one base station to another. Specifically, the terminal reports the signal strength of surrounding base stations to a serving base station. The serving base station prepares a target base station to which the terminal will perform a handover, based on the signal strength report from the terminal, and orders the terminal to perform a handover. Upon receiving a handover command message from the serving base station, the terminal immediately performs a handover to attempt a connection to the target base station.
However, if a radio link in a handover area (temporal area or spatial area) is in a bad condition, it is difficult to transmit the signal strength report from the terminal to the serving base station in real time, and it is also difficult to transmit the handover command from the serving base station to the terminal in real time. Due to this, data interruption time during handover increases, and communication quality drops at the time of handover.
Moreover, the terminal triggers a handover only when the signal strength of the target base station is somewhat higher than the signal strength of the serving base station. Accordingly, where the signal strength of the target base station is slightly higher than the signal strength of the serving base station when the signal strength of the serving base station is not high, the terminal does not trigger a handover. Due to this, a radio link failure (RLF) may occur. After the occurrence of an RLF, the terminal performs an operation for selecting the target base station's cells to recover the RLF. Data is interrupted during this operation, causing the communication quality to drop.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.